A Phenomenal Galaxy (Science Advent 8)

Day 8

The radio galaxy Hercules A, seen in visible light (the galaxy at the center, background galaxies) and radio light, which shows the huge jets of matter streaming from the galaxy’s central black hole. [Credit; NASA, ESA, S. Baum & C. O’Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF),and the Hubble Heritage Team (STScI/AURA)]

In visible light, the galaxy known as Hercules A doesn’t look all that special. It’s an elliptical galaxy, which lacks the beautiful arms and other structures of spiral galaxies. However, in radio light, Hercules A suddenly exhibits huge plumes of plasma streaming from its center. These jets are each about a million light-years long, much larger than the galaxy itself, as you can see in the image above. The source of these jets is the black hole at the center of Hercules A, which is about a thousand times more massive than the black hole at the heart of the Milky Way.

In fact, as I promised, the radio image of the galaxy (the stuff in red in the photo above) was produced by the Very Large Array (VLA), a collection of 27 telescopes, each 25 meters in diameter. By working as a single unit, the telescopes in the VLA can map the structures within the plasma jets, revealing their billows, strikingly visually similar (though less turbulent in the absence of air) to those of an extinguished candle.